Manipulating Spin-Orbit Coupling in Conjugated Microporous Polymers Through Torsion Engineering to Generate Efficient...

Maximizing photon utilization in organic photocatalysis requires harnessing both singlet and triplet excitons, however, the strategies to populate the spin-forbidden triplet state in metal-free polymers are rare. To address this issue, we report a new strategy, namely employing a spin-orbit charge transfer intersystem crossing (SOCT-ISC), to unlock the triplet manifold in conjugated microporous polymers (CMPs). Using a postsynthetic [2 + 2] cycloaddition-retroelectrocyclization (CA-RE) reaction, we precisely control the cyano number in the polymer backbone. This chemical modification induces a critical orthogonal molecular torsion, which maximizes spin-orbit coupling (SOC) and minimizes the singlet-triplet energy gap (ΔE_ST). Femtosecond transient absorption spectroscopy confirms the efficient triplet generation by torsion engineering. Consequently, the optimized photocatalyst achieves a hydrogen peroxide (H₂O₂) production rate of 5.01 mmol g^-1 h^-1 in pure water and a rate of 101.26 mmol g^-1 h^-1 in a benzyl alcohol-coupled system, with a solar-to-chemical conversion (SCC) efficiency of 0.62%, and an outdoor production reaches 5 mmol L^-1 daily. This work leverages torsion engineering to harness triplet excitons, demonstrating the successful overcoming of thermodynamic barriers in artificial photosynthesis.